CSF + Hydrocephalus

Question 1

What is hydrocephalus?

Answer 1

General terms for condition whereby there is excess CSF within the intracranial space and interventricular spaces

This causes dilation of the ventricles and a wide range of symptoms

Question 2

How is CSF produced?

Answer 2

Choroid plexus through metabolically active process whereby sodium is pumped into the subarachnoid space, and water follows from the blood vessels

Question 3

How much CSF does the average adult brain produce daily?

Answer 3

450 - 600 cc

Question 4

How much CSF is present within the brain at any given time?

Answer 4

150 cc (with 25 cc in the ventricles)

The CSF volume turns over three to four times every day, with only a very small fraction of the CSF being in the ventricles at any given time, even though the majority of it is produced there

Question 5

Describe the CSF pathway

Answer 5

1. Produced in lateral ventricle and travels through to the interventricular foramen
2. Flows through 3rd ventricle and then passes through the cerebral aqueduct
3. Enters the 4th ventricle and exits either of two Foramina of Luschka or single Foramen of Magendie
4. CSF flows through subarachnoid space and is eventually reabsorbed into the venous systems through arachnoid granulations along the dural venous sinuses

Question 6

How is CSF absorbed?

Answer 6

CSF resorption is a passive process that is driven by the pressure gradient between the intracranial space (ICP) and the venous system (CVP) - ICP > CVP

Arachnoid granulations contain arachnoid villi, which function as pressure-dependent one-way valves that open when the ICP is ~3 to 5 cm H20 greater than dural venous sinus pressure

Question 7

What are the three types of hydrocephalus?

Answer 7

• Communicating hydrocephalus (CoH) - non-obstructive
• Non-communicating hydrocephalus (NCH) - obstructive
• Normal Pressure Hydrocephalus (NPH)

Question 8

What is the difference between CoH and NCH?

Answer 8

In CoH, the CSF can travel freely through the pathway. NHC is when the CSF cannot travel freely as there is an obstruction.

Question 9

What happens in CoH?

Answer 9

It is usually due to a problem with CSF resorption and cannot keep up with how much CSF is being produced.

As a result, the ventricular system dilates informally and ICP rises.

Rarely, there is an overproduction of CSF (rather than under-absorption)

Question 10

What can cause over production of CSF in communicating hydrocephalus?

Answer 10

Choroid plexus papillomas

Question 11

What are the signs/symptoms of CoH?

Answer 11

In children whose cranial sutures haven’t fused —> disproportional increase in head circumference or failure to thrive.

Increased intracranial
pressure:
• Headache 
• Nausea + vomiting 
• Papilledema 
• Gait disturbance 
• 6th cranial nerve palsy 
• Upgaze difficulty

Question 12

Why does ICP cause 6th nerve palsy?

Answer 12

6th nerve palsy because it has the longest intercranial course so affected with raised IC pressure

Question 13

What is papilledema?

Answer 13

Optic nerve swelling due to increased ICP

Question 14

Is the onset of communicating hydrocephalus slow or fast?

Answer 14

Usually it is a gradual onset, but a sizeable insult can cause an acute disruption of balance between CSF production and resorption, and resorption is suddenly reduced.

Question 15

When does NCH occur?

Answer 15

Whenever there in ANY physical obstruction to the normal flow of CSF before it leaves the ventricles

Question 16

What can radiography show?

Answer 16

• Dilation of the temporal horns of the lateral ventricles - in most patients these should be almost invisible
• Third ventricle will become ballooned
• Peripheral sulci disappear

Question 17

What is used to determine if the ventricle in the brain are abnormally enlarged on a scan?

Answer 17

• Evans ration - ratio of ventricle size compared to brain width >30%
• Ventricular index: >50%

Question 18

What is the treatment of hydrocephalus?

Answer 18

Surgical:

1. External Ventricular Drain (EVD) - catheter passed through the patient’s skull into the lateral ventricle
2. Shunt

Question 19

What is the problem with use of EDV to treat acute hydrocephalus?

Answer 19

Cannot be maintained and so a permanent shunt will be required. High infection risk.

Question 20

What is the treatment for NCH?

Answer 20

• NCH treatment also surgical, but sometimes shunt can be avoided by removing the obstructing lesion
• Shunt
• Third ventriculostomy

Question 21

Is a shunt always necessary in CoH?

Answer 21

In acute situations, may only require EDV for ~10days - 2weeks

Question 22

What is a third ventriculostomy?

Answer 22

Hole is surgically opened in floor of third ventricle so CSF flows out to bypass the cerebral aqueduct

Question 23

Name some reasons for why a VP shunt might fail?

Answer 23

Mechanical failure from occlusion/disconnection, migration, overdrainage/underdrainage, infection or skin erosion

Question 24

Why is NPH clinically significant?

Answer 24

Because it is a rare preventable and/or reversible causes of dementia

Under-recognition leads to many patients with NPH to be diagnosed with Alzheimer’s or age related dementia and never seek treatment

Question 25

What are the signs/symptoms of NPH?

Answer 25

Hakim-Adams Triad:
• Urinary incontinence
• Gait disturbance - wide stance, short, shuffling step
• Progressive dementia

Question 26

What investigations are used for NPH?

Answer 26

CT/MRI:
• Will look like communicating hydrocephalus

Lumbar Puncture:
• Normal opening pressure
• Improves symptoms with CSF removal
• Gait assessment and MMSE

Question 27

What is the treatment for NPH?

Answer 27

Programmable VP shunt placement.

LP shunts tend to overdrain and are difficult to assess and revise, where VP are very sensitive to pressure changes.